Is barley yield in the UK sink limited?: II. Factors affecting potential grain size

In the absence of serious post-anthesis stress, the potential supply of assimilates for grain filling in barley appears to exceed the storage (sink) capacity of the grains. The sink capacity is a function of the number of grains per unit land area and their potential size. In order to investigate the contribution of pre and early post-anthesis factors in the control of potential grain weight, regression analysis has been used to analyse data from field experiments conducted on winter barley crops cv. Pearl grown at six sites across the UK between 2002 and 2004. Crops were grown under a comparable husbandry regime with a full crop protection, growth regulator and fertilizer programme. The mean grain weight (MGW) varied from 35 to 46 mg at 100% dry matter over 17 site/year combinations. The variation in MGW between site/years was associated with differences in the rate rather than the duration of grain filling. MGW did not relate well to any measure of above ground growth or crop structure at ear emergence (Zadoks GS59). There was a significant positive linear relationship between MGW and the amount of radiation (PAR) intercepted per unit grain number between ear emergence and the start of rapid grain filling (r² = 0.32, P = 0.023), but not over the whole grain filling period. This is consistent with the view that MGW is determined by potential grain size. A multiple regression model comprising five explanatory variables accounted for a much larger proportion of the total variation in MGW (r² = 0.72, P = 0.013) than PAR interception on its own. There were significant positive associations of MGW with post-anthesis radiation use efficiency and PAR intercepted from GS59 to the start of rapid grain growth (RGG), and significant negative associations with the shoot number per plant, mean air temperature from GS39–59 and mean daily rainfall from GS59-RGG. The results suggest that both pre and post-anthesis conditions operate in concert to determine the potential grain weight of barley in temperate climates. The dry weight and water content of grains and ears followed a common pattern during grain growth for all site/years when the percentage moisture content was used as an index to normalise different rates of development. Use of the above data for predicting potential grain weight of barley prior to harvest is discussed.     

How weed control and fertilisation influence tree physiological processes and growth at early establishment in an exotic F<Subscript>1</Subscript> hybrid pine plantation of subtropical Australia

Purpose

This study investigated how nitrogen (N) nutrition and key physiological processes varied under changed water and nitrogen competition resulting from different weed control and fertilisation treatments in a 2-year-old F₁ hybrid (Pinus elliottii Engelm var. elliottii?×?P. caribaea var. hondurensis Barr. ex Golf.) plantation on a grey podzolic soil type, in Southeast Queensland.

Materials and methods

The study integrated a range of measures including growth variables (diameter at ground level (DGL), diameter at breast height (DBH) and height (H)), foliar variables (including foliar N concentration, foliar δ¹³C and δ¹⁵N) and physiological variables (including photosynthesis (A_n), stomatal conductance (g_s), transpiration (E), intrinsic water use efficiency (WUE_i) (A/g_s) and xylem pressure potential (Ψ_XPP)) to better understand the mechanisms influencing growth under different weed control and fertilisation treatments. Five levels of weed control were applied: standard (routine), luxury, intermediate, mechanical and nil weed control, all with routine fertilisation plus an additional treatment, routine weed control and luxury fertilisation. Relative weed cover was assessed at 0.8, 1.1 and 1.6 years after plantation establishment to monitor the effectiveness of weed control treatments. Soil investigation included soil ammonium (NH₄ ⁺-N), nitrate (NO₃ ^?-N), potentially mineralizable N (PMN), gravimetric soil moisture content (MC), hot water extractable organic carbon (HWETC), hot water extractable total N (HWETN), total C, total N, stable C isotope composition (δ¹³C), stable N isotope composition (δ¹⁵N), total P and extractable K.

Results and discussion

There were significant relationships between foliar N concentrations and relative weed cover and between tree growth and foliar N concentration or foliar δ¹⁵N, but initial site preparation practices also increased soil N transformations in the planting rows reducing the observable effects of weed control on foliar δ¹⁵N. A positive relationship between foliar N concentration and foliar δ¹³C or photosynthesis indicated that increased N availability to trees positively influenced non-stomatal limitations to photosynthesis. However, trees with increased foliar N concentrations and photosynthesis were negatively related to xylem pressure potential in the afternoons which enhanced stomatal limitations to photosynthesis and WUE_i.

Conclusions

Luxury and intermediate weed control and luxury fertilisation positively influenced growth at early establishment by reducing the competition for water and N resources. This influenced fundamental key physiological processes such as the relationships between foliar N concentration, A _n, E, g_s and Ψ_XPP. Results also confirmed that time from cultivation is an important factor influencing the effectiveness of using foliar δ¹⁵N as an indicator of soil N transformations.

     

Importance of extensional rheological properties on fiber-enriched corn extrudates

Incorporation of insoluble fibers into extruded cereals severely limits their expansion and reduces crispness. The specific objective of this work was to investigate how corn bran and its fractions mixed with cornmeal affect rheology and extrudate expansion. Alkali-treated bran (ATB) and alkaline-soluble bran (ASB) were prepared from unmodified corn bran (UMB). Mixtures of the different corn bran fractions and degermed cornmeal having a 26% (w/w) of total dietary fibers were extruded in a twin screw extruder and expansion of the extrudates was determined. Melt shear rheology of mixtures of cornmeal and different corn bran fractions having a 20% total dietary fiber was determined using a capillary rheometer at 120 °C while the extensional rheology was determined using lubricated squeezing flow. The expansion of extrudates containing ATB was larger than those containing UMB, while extrudates containing ASB showed a greater expansion that was close to that of the control. Addition of UMB to cornmeal increased shear and extensional viscosity significantly as compared to the control. ATB addition increased the shear viscosity of the mixture to a small extent but showed the highest extensional viscosity amongst the samples. Addition of ASB resulted in mixtures having lower shear and extensional viscosities than the control.     

DUPLEX-ULTRASONOGRAPHIC EVALUATION OF THE COMMON CAROTID ARTERY IN THE RESTING, SEDATED AND ANESTHETIZED HORSE

The aim of this study was to determine the blood flow in the carotid artery during halothane anaesthesia by means of duplex-sonography. Seventeen warm blood horses were evaluated in dorsal and lateral recumbency and the results were compared with the values of the same horses resting and under sedation. The cross sectional area of the vessels, the time-averaged maximal blood velocity, time-averaged maximal blood flow and the resistance index were determined and the flow profile was evaluated. During halothane anesthesia the total blood flow shows a significant increase which is not dependent on the positioning of the horse. Mean blood velocity is decreased by sedation and significantly increased during anesthesia. Reduced peripheral resistance is expressed by a decline of the resistance index. After sedation and during recumbency there is an increase in diameter of the carotid artery.     

Temporal changes in chemical properties of air‐dried stored soils and their interpretation for long‐term experiments

The usefulness of stored soils from long‐term experiments is often questioned because of changes that might occur during storage. We examined changes during long‐term storage (8–69 years) in the chemical properties of soils with a range of pH values (3.4–8.1 in water) from woodland and grassland experiments at Rothamsted Experimental Station in the UK. No significant changes during storage were measured for total C and N. Large but erratic changes in exchangeable Na⁺ content between 1959 and 1991 were probably caused by contamination of the 1959 samples by perspiration and from sodium‐based glassware. Exchangeable K⁺ increased during storage but only by a small amount. Small changes in exchangeable Ca²⁺ and Mg²⁺ were measured in some samples but not in others. Generally the amount of exchangeable cations increased slightly during storage. This is probably linked to the decreases of 0.4 units in the pH of acid soils, which we attribute to the hydrolysis of approximately 0.25% of the exchangeable Al³⁺. A doubling of the amount of exchangeable Mn²⁺ during storage for 32 years was probably caused by re‐equilibration of Mn species. The most practicable way to prepare soil samples for long‐term storage is to dry them in air. However, those who study changes in soil by re‐analysing samples of the soil stored for a long time must (i) use the same methods of analysis, or (ii) demonstrate that different methods lead to the same results, and (iii) know what changes can arise during storage.     

Equine neonatal septicaemia: 24 cases

Equine neonatal septicaemia was confirmed in 24 foals hospitalised at the Rural Veterinary Centre between 1989 and 1992 with suspected septicaemia. Septicaemia was confirmed by culture of bacteria from blood of live foals and tissues obtained at necropsy of foals that died or were euthanased. Pathogenic bacteria isolated were predominantly Enterobacteriaceae (including Escherichia coli and Salmonella serovars) and Actinobacillus equuli. Clinical manifestations of septicaemia included signs of depression, dehydration, abnormalities in body temperature and manifestations of localised infection including diarrhoea, pneumonia, and septic arthritis. Most common haemato-logical abnormalities were neutropenia and increase of circulating band neutrophils. Survival rate of foals with confirmed septicaemia was 70.8%. Survival was found to be less likely in the presence of pneumonia, severe signs of depression, marked haematological changes or septic arthritis at the time of admission. Seven foals were confirmed to have septic arthritis without concurrent septicaemia. Of these, 4 had multiple joint involvement. Bacteria isolated from infected joints were predominantly Salmonella serovars. Four foals with septic arthritis failed to survive, due to multiple joint infection, which was unresponsive to treatment. The clinical and haematological abnormalities present in foals with confirmed septicaemia and septic arthritis were consistent with those observed in other studies. The bacterial isolates from foals with confirmed septicaemia were similar to those isolated in other studies. In contrast, the bacteria isolated from foals with septic arthritis without concurrent septicaemia were different from other studies.     

CT FEATURES OF ALVEOLITIS AND SINUSITIS IN HORSES

Sinusitis is a common disorder in horses and may result from trauma, dental diseases, or space-occupying lesions. Radiography can only provide a limited amount of information. Computed tomography (CT) has been documented as an alternative imaging method. Eighteen horses (mostly Warmblood) with signs of chronic sinusitis were examined preoperatively with CT to assist in diagnosis of the underlying cause. There was a group of common CT features in horses with dental disease and sinusitis. The first molar was the most frequently affected maxillary cheek tooth. Hypoattenuation of the cementum, destruction of the enamel, and filling of the infundibular cavity with gas were the most frequent CT findings associated with caries. Gas bubbles within the bulging root area or fragmentation of the root in combination with swelling of the adjacent sinus lining were the most important CT features of dental decay. CT findings associated with sinusitis included excessive thickening of the respiratory epithelium in the rostral maxillary sinus; the caudal maxillary sinus was less often involved. The infraorbital canal, the nasomaxillary duct, and the frontomaxillary aperture were usually involved. The maxillary bone, however, especially the facial crest, was involved in nearly every horse, being characterized by endosteal sclerosis, thickening, periosteal reaction, and deformation leading to facial swelling in chronic infections. CT images allowed identification of involvement of individual teeth more clearly to reveal the diseased one for treatment. Three-dimensional imaging allowed improved understanding of the extent and severity of the pathologic change.     

Progressive ethmoidal haematoma in horses

Progressive ethmoidal haematoma was diagnosed in 12 Thoroughbreds, 1 part- Arab and 1 stock horse. Ages ranged from 3 to 18 years and both males and females were affected. Diagnosis was based on history, clinical signs, endoscopic and radiographic findings, and was confirmed histologically in 10 cases. Eleven (78%) of the lesions were unilateral and 3 (22%) were bilateral. Two horses were euthanased on diagnosis, 4 were treated conservatively. Of the latter, 3 were euthanased 6 to 24 months after diagnosis, due to progression of the lesions, while 1 case resolved completely within 13 months. Eight horses were treated by surgical excision of the lesion. Three died in the post-operative period, 3 were euthanased within 48 months after recurrence of the condition, and 2 had no recurrence within 60 and 72 months, respectively.     

Adrenalectomy of sheep: a novel technique

A rapid technique for adrenalectomy of sheep was developed. Bilateral adrenalectomy was performed in a single stage operation by inducing ischaemia with latex rings of the type used commonly for the castration of lambs and calves. The success of the technique was demonstrated by failure of exogenous ACTH to increase circulating cortisol concentrations. Adrenal steroid replacement was used to maintain the sheep during the post-operative period (cortisol 0.25 mg.kg^-1, deoxycorticosterone acetate 0.05 mg.kg^-1). Adrenalectomised sheep were maintained for up to 20 days without glucocorticoid, provided a lowered dose of mineralocorticoid was administered (0.04 mg.kg^-1***day^-1). Adrenalectomised sheep had significantly (P < 0.007) lower packed cell volume (23.75%) than normal sheep (31.24%), across a broad range of cortisol concentrations (0 to 734 ng/mL), indicating that plasma cortisol may not reflect true blood concentrations when drawing comparisons between adrenalectomised and normal sheep.